Temperature independent magnetorheological materials

• US 5,599,474 A
• Filed: 04/18/1994
• Issued: 02/04/1997
• Est. Priority Date: 10/30/1992
• Status: Expired due to Term

• Current Assignee: Lord Corporation (Parker-Hannifin Corporation)
• Original Assignee: Lord Corporation (Parker-Hannifin Corporation)
• Inventors: Weiss, Keith D., Duclos, Theodore G., Carlson, J. David, Abbey, Kirk J.
• Primary Examiner(s): Willis, Jr., Prince
• Assistant Examiner(s): Diamond, Alan D.
• Application Number:
  US08/229,270
• Time in Patent Office: 1,023 Days
• Field of Search: 252/62.52, 252/62.54, 252/62.56, 252/74, 252/75
• US Class Current: 252/62.52
• CPC Class Codes: H01F 1/447 characterised by magnetoviscosity, e.g. magnetorheological, magnetothixotropic, magnetodilatant liquids electrorheological fluids C10M171/001

Abstract

A magnetorheological material containing a particle component and a carrier fluid or mixture of carrier fluids having a change in viscosity per degree temperature (Δη/ΔT ratio) less than or equal to about 16.0 centipoise/°C. over the temperature range of about 25° C. to -40° C. The magnetorheological material exhibits a substantial magnetorheological effect and excellent lubricating properties with a minimal variation in mechanical properties with respect to changes in temperature. The magnetorheological material is advantageous in that it provides for the design of devices that are smaller, more efficient and consume less power.

Claims

1. A magnetorheological material comprising:

a) a carrier fluid selected from the group consisting of silicon oils and having a Δ

η

/Δ

T ratio less than or equal to about 16 centipoise/°

C. over a temperature range of about -40°

to 25°

C.; and

,

b) a particle component wherein said particle component consists of particles having diameters from about 1.0 to 250 microns and having magnetorheological activity, wherein said magnetorheological material exhibits minimal variation in force output over a temperature range from about -40°

C. to 150°

C.

2. A magnetorheological material according to claim 1 wherein said silicone oils are selected from the group consisting of polydimethylsiloxanes, polymethylphenylsiloxanes, poly(methyl-3,3,3-trifluoropropyl)siloxanes, polycholorophenylmethylsiloxanes, dimethyl(tetrachlorophenyl)siloxane copolymers, dimethyl(phenylmethyl)siloxane copolymers, dimethyl(diphenyl)siloxane copolymers, and methyl-3,3,3-trifiuoropropyl (dimethyl )siloxane copolymers.

3. A magnetorheological material according to claim 1 wherein the Δ

η

/Δ

T ratio is less than or equal to about 9 centipoise/°

C.

4. A magnetorheological material according to claim 3 wherein the Δ

η

/Δ

T ratio is less than or equal to about 7 centipoise/°

C.

5. A magnetorheological material according to claim 1 wherein the particle component is selected from the group consisting of iron, iron alloys, iron oxide, iron nitride, iron carbide, carbonyl iron, chromium dioxide, low carbon steel, silicon steel, nickel, cobalt, and mixtures thereof.

6. A magnetorheological material according to claim 1 wherein the particle component is covered by a surface barrier coating.

7. A magnetorheological material according to claim 6 wherein the barrier coating is composed of a material selected from the group consisting of nonmagnetic metals, ceramics, thermoplastic polymeric materials, thermosetting polymers and combinations thereof.

8. A magnetorheological material according to claim 1 further comprising a surfactant.

9. A magnetorheological material according to claim 1 further comprising a thixotropic additive selected from the group consisting of hydrogen bonding thixotropic agents and colloidal additives.

10. A magnetorheological material according to claim 1 wherein the carrier fluid is present in an amount ranging from about 50 to 95 percent by volume and the particle component is present in an amount ranging from about 5 to 50 percent by volume of the total magnetorheological material.

11. A magnetorheological material according to claim 10 wherein the carrier fluid is present in an amount from about 60 to 85 percent by volume and the particle component is present in an amount from about 15 to 40 percent by volume of the total magnetorheological material.

12. The magnetorheological material of claim 1 wherein said particle component consists of particles having diameter from about 1.0 to 50 microns.

13. A magnetorheological material according to claim 1 wherein said silicon oil has a viscosity within the range of 20 to 200 centipoise at 25°

C.

15. A magnetorheological material according to claim 1 wherein the glycol esters and ethers are propylene or ethylene glycol derivatives containing the basic structure:

##STR3## wherein A is H or CH₃ ;

B is CH₃, H, OH, or O₂ CR with R being an alkyl or aryl group;

B'"'"' is H, CH₃ or C(O)R'"'"' with R'"'"' being an alkyl or aryl group; and

x ranges from about 1 to 8.

14. A magnetorheological material comprising:

a) a carrier fluid selected from the group consisting of glycol esters and ethers and having a Δ

η

/Δ

T ratio less than or equal to about 16 centipoise/°

C. over a temperature range of about -40°

C. to 25°

C. and,

b) a particle component wherein said particle component consists of particles having diameters from about 1.0 to 250 microns and having magnetorheological activity, wherein said magnetorheological material exhibits minimal variation in force output over a temperature range from about -40°

C. to 150°

C.

16. A magnetorheological material comprising:

a) a carrier fluid selected from the group consisting of monobasic acid esters and having a Δ

η

/Δ

T ratio less than or equal to about 16 centipoise/°

C. over a temperature range of about -40°

to 25°

C. and,

b) a particle component wherein said particle component consists of particles having diameters from about 1.0 to 250 microns and having magnetorheological activity, wherein said magnetorheological material exhibits minimal variation in force output over a temperature range from about -40°

C. to 150°

C.

17. A magnetorheological material comprising:

a) a carrier fluid selected from the group consisting of silicate esters and having a Δ

η

/Δ

T ratio less than or equal to about 16 centipoise/°

C. over a temperature range of about -40°

to 25°

C. and,

b) a particle component wherein said particle component consists of particles having diameters from about 1.0 to 250 microns and having magnetorheological activity, wherein said magnetorheological material exhibits minimal variation in force output over a temperature range from about -40°

C. to 150°

C.

18. A magnetorheological material comprising:

a) a mixture of carrier fluids wherein the mixture of carrier fluids has a Δ

η

/Δ

T ratio less than or equal to about 16 centipoise/°

C. over a temperature range of about -40°

C. to 25°

C.; and

,

b) a particle component wherein said particle component consists of particles having diameters from about 1.0 to 250 microns and having magnetorheological activity, wherein said magnetorheological material exhibits minimal variation in force output over a temperature range from about -40°

C. to 150°

C.

19. A magnetorheological material according to claim 18 wherein said mixture of carrier fluids consists of a mixture of a Group I carrier fluid selected from the group consisting of unsaturated hydrocarbon oils, glycol esters and ethers, fiuorinated esters and ethers, and silicone oils and a Group II carrier fluid selected from the group consisting of natural fatty oils, mineral oils, dibasic acid esters, synthetic cycloparaffins and synthetic paraffins, unsaturated hydrocarbon oils, glycol esters and ethers, fiuorinated esters and ethers and silicone oils, said Group II carrier fluid having a Δ

η

/Δ

T ratio greater than about 16 centipoise/°

C. over a temperature range from about -40°

C. to 25°

C.

20. A magnetorheological material according to claim 19 wherein the Group I and Group II carrier fluids are present in a Group I:

Group II weight ratio of about 85;

15.

21. A magnetorheological material according to claim 20 wherein the ratio is about 75:

25.

22. A magnetorheological material according to claim 21 wherein the ratio is about 50:

50.

23. A magnetorheological material according to claim 18 wherein said mixture of carrier fluids consists of a mixture of a Group III carrier fluid selected from the group consisting of synthetic cycloparaffins and synthetic paraffins and a Group IV carrier fluid selected from the group consisting of natural fatty oils, mineral oils, dibasic acid esters, unsaturated hydrocarbon oils, glycol esters and ethers, and fiuorinated esters and ethers.

24. A magnetorheological material according to claim 23 wherein the Group III and Group IV carrier fluids are present in a Group III:

Group IV weight ratio of about 85;

15.

25. A magnetorheological material according to claim 24 wherein the ratio is about 75:

25.

26. A magnetorheological material according to claim 25 wherein the ratio is about 50:

50.